Electric water heater



Aug. 9, 1949. c. M. osTERHr-:LD 2,478,499

ELECTRIC WATER HEATER Filed May 29, 1946 2 sheets-sheet 1 U 323ym f2 -5 n Ey-j 25 j INVEN TOR.

CLARK M.- STERHELD BY @y-(J4 ATTY All@ 9, 1949- c. M. osTERHELD 2,478,499

ELECTRI C WATER HEATER yFiled May 29, v194e; 2 sheets-sheet 2 INVENTOR.

CLARK M. OSTERHELD AT T'Y Patented Aug. 9, 1949 ELECTRIC WATER HEATER Clark M. Osterheld, Stoughton, Wis., assigner to McGraw Electric Company, Elgin, Ill., a corporation of Delaware Application May 29, 1946, Serial No. 673,208

Claims. 1

My invention relates to electric water heaters and particularly to a novel form of resistor for such heaters and to its mounting on a domestic hot water tank.

An object of my invention is to provide a relatively simpl'e and highly elicient electric heater for domestic hot water tanks.

Another object of my invention is to provide an electric heater including, highly efficient means for conducting the heat generated in the resistor to the tank.

Another object of my invention is to provide a metallic resistor for an electric heater and a hot water tank that shall be applicable to either the outside or to the inside surface of a tank.

Another object of my invention is to provide a metallic resistor for the heater and a water tank, that shall have thereon a relatively thin integral, inorganic, heat-conducting, high-temperatureresisting, and electric-insulating coating.

Other objects of my invention will either be apparent from a description of several diiierent forms of device, each embodying my invention, or will be set forth in detail hereafter and pointed out particularly in the appended claims.

In the drawings.

Figure 1 is a view, in vertical section, through a domestic hot water tank having operatively associated therewith an electric heater embodying my invention,

Fig. 2 is a horizontal, sectional view therethrough taken on the line 2 2 of Fig.1,

Fig. 3 is a view in side elevation on an enlarged scale, taken on the line 3-3 of Fig. 2,

Fig. 4 is a top plan View of a metallic resistor comprising a part of my invention,

Fig. 5 is a fragmentary view similar to Fig. 1 showing the mounting of my improved electric heater on the outside of the tank,

Fig. 6 is a view in side elevation thereof taken on the line 6-6 of Fig. 5,

Fig. 7 is a still further modiiication of an electric heater embodying my invention,

Fig. 8 is a view in section therethrough taken on the line 8--8 of Fig. 7, and,

Fig. 9 is a fragmentary view showing a still further modiiication of my device.

Referring first of all to Fig. 1 of the drawings I have there illustrated a domestic hot water tank I I which is provided with a lower cold water inlet pipe I 3 and an upper hot water outlet pipe I5. It is surrounded by a mass I'I of heat'dnsulating ma* terial, which heat-insulating material held in proper operative position by an outside casing I9, which casing is supported by two feet 2l and which supports the tank i i as by blocks 25.

I provide an electric heater comprising a flat metallic resistor member strip 25 which, as is shown in Fig. 4 of the drawings, comprises a plurality of straight convolutions, the two adjacent end portions of which are connected to each other, the width end thickness of each of the substantially straight convolutions 25 being such that the resistance of the resistor member 25 will permit of a current traversing the resistor member to give the desired wattage. I may mention that the thickness of the metallic resistor member 25 may fbe on the order of .01 inch to .02 inch, and while I may make the metallic resistor member 25 of aluminum, I am not limited thereto but may use metallic resistor material now utilized in the art.

I provide a metallic member 21 which may be of thin sheet metal such as aluminum or steel and I weld the edges of the member 21, which is of iiattened, shallow channel shape in lateral section, against the inner wall of tank I I as by continuous welding seams 29.

I provide further a relatively thin sheet 3I which is preferably made of aluminum and has a thickness on the order of .01 inch or .015 inch and has a width sufficient to cover the surface of the tank and iit closely within the member 2l of channel shape.

I provide on the entire outer surface of the flat metallic resistor member 25, on the inner surface of the member 2l, of channel shape, as well as on the entire outer surface of member 3i an integral, inorganic, heart-conducting, high-temperature-resisting, and electric-insulating coating made in accordance with U. S. Patent No. 1,526,127. rhe metallic resistor member 25 is iirst shaped to substantially circular form and having a diameter which is somewhat less than the diameter of the inner surface of the tank Il so that when it is positioned inwardly through an opening 33 provided in the tank, the tendency of the resistor member 25 will be to closely engage the inner surface of the spacing strip 3I. The resistor member unit 25 may be provided with two extensions 35 so that electric connections may be made to the resistor in a well-known manner.

Referring now to Figs. 5 and 6 I have there shown a member 3l of iiattened, shallow channel shape in lateral section, the side portions of member 3l being welded into close engagement with the outside surface of tank II by seams 39. I provide a strip 4I which is preferably but not necessarily made of relatively thin aluminum having a thickness on the order of .01 to .015" and locate the same between a resistor 43 and the outside surface of tank I I.

Referring to the resistor member 43 in Figs. 5 and 6 which is of the same character as resistor 25, the entire outer surface of the resistor is covered with a relatively thin integral, inorganic, heat-conducting, high temperature resisting, and electric-insulating coating substantially as hereinbefore set forth in connection with resistor nel shape as well as an entire outer surface of strip lll is also covered with substantially the same kind of coating. One method of making such a coating on the surface of a member of aluminum is set forth in Patent No. 1,526,127, but other wellknown methods usable in case of change from aluminum to steel may also be usedr .The thick,- ness of said coating may be on the order of .001".

Referring now to Figs. 7 and 8 I` have there shown an electric tank heater extending substantially vertically of the tank. A metallic member 45, of relatively flat, shallow channel shape has its vertical edges welded against the outer surface of a tank. While I have shown four such members, I do not desire to be limited thereto. A metal plate 4l, preferably of aluminum and having a thickness on the order of .015 is positioned betweena resistor' and the outer surface of the tank. The innersurface of member 45, the entire outer surface of spacing plate 41 and of resistor member 49 has thereon an integral, inorganic, heat-conducting, high-temperature-resisting and electric-insulating coating, the thickness of which is on the order of .001.

Referring now to Fig. 9 of the drawings I have there shown a hot water tank ll having welded against its inner surface a member 5l of flattened, shallow channel shape as by weldingseams 53. A resistor 55 of substantially the same kind as resistor 25V in Fig. 4 is positionedY within a i member 57 whichis vof attened tubular Yshape and the inner surface of which closely engages the outer surface of resistor 55. The resistor 55 as well as its enclosing tubular member 5l may be made of aluminum and the thickness thereof v is on the order of .01" to .015".

The device embodying my invention shows structures utilizing a relatively thin metallic resistor member having over its entire outer surface a thin integral, inorganic, heat-conducting, hightemperature-resisting, and electric-insulating coating, the thickness of which is on the order of .001". I have found that the temperature differ- Y entia1 between the temperature of the resistor Y heat ow path adjacent the water byv an amount on the order of 400 F'.

Themembers 21, 31, 15 and 5| may be made of copper or of aluminum, the latter material having light-weight as well. as high-heat conductivity, the same as copper. The welding of these members to the tank need not be water-tight in case they are welded against the outside surface of the tank but are preferably made water-tight. The path of the flow of heat from the resistor to the water is directly inwardly from the resistor and through the side portions of the sheaths of channel shape. -While these side portions have beenV shown relatively narrow, I may widen them to reduce the amount of heat carried by a unit area. The depth of these sheaths of channel shape is just sufficient to receive the resistor and the spacing strip or the flattened tubular member. In case the heating unit is located inside the tank the sheath must be welded tothe tank ina watertight manner.

Y The. thickness and the width of the individual inorganic, heat-conducting,

convolutions of the resistor member may be made such as to give the desired ohmic resistance. However, instead of forming the resistor out of a sheet, I may use a. conductor strip forming it to comprise substantially straight end connected convolutions, the general appearance of which will be substantially the same as shown in Fig. 4.

Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof and all Such modifications clearly coming within the scope of the appended claims shall be considered as covered thereby.

I claim as my invention:

1. A hot water tank of metal having a imperforate metallic member of flattened channel shaped in lateral section secured thereto in a water-tight manner against its inner surface and a flat metallic resistor member in said member of channel shape, said resistor member having on its entire outer surface an integral, inorganic, heat-conducting, high-temperature-resisting and electric-insulating coating.

2. An iron hot water tank having a metallic member of at channel shape in lateral section secured thereto in a water-tight manner against its inner surface, a fiat metallic resistor member in said member of channel shape and a spacing strip of aluminum between said resisto-r and said tank, the entire outer surface of said spacing strip and of said resistor member and the inner surface of the intermediate portion of said member of channel shape having thereon an integral, inorganic, heat-conducting, high-temperatureresisting and electric-insulating coating.

3. A hot water tank of iron having a metallic member of shallow channel shape in lateral section secured thereto in a water-tight manner against its inner surface to provide a shallow space between said metallic member and the wall of the tank, a flat, thin metallic resistor within said member of channel shape and a spacing strip of aluminum between the tank and said resistor,I said resistor and spacing strip each having on its entire outer surface an integral,

high-temperatureresisting and electric-insulatingcoating.

4. The combination of the immediately preceding claim wherein said resistor contains aluminum and wherein the coating of said resistor and spacing strip includes oxidation products of aluminum.

5. A hot water tank of iron having a metallic member of shallow channel shape in lateral section secured thereto in a water-tight manner against its inner surface to provide a shallow space between said metallic member and the wall of said tank, a flat thin metallic resistor within said space constituting a heater for said tank, and means for electrically insulating said resistor from said metallic member and said tank.

CLARK M. OSIERHELD.

REFERENCES CITED rihe following references are of record in the le of this patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,478,499 August 9, 1949 CLARK M. OSTERHELD It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 2, for the Word end read and;

and that the said Letters Patent should be read with this correction therein that the f d same may conform to the record of the case in the Patent Oice.

Signed and sealed this 28th day of Merch, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent No. 2,478,499 August 9, 1949 CLARK M. OSTERHELD It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 2, for-"the Word end read and;

and tha-t the said Letters Patent should be read With this correction therein that the same may conform to the record of the case in the Patent Oice. v

Signed and sealed 'this 28th dey of Merch, A. D. 1950.

THOMAS F. MURPHY,

yAssistant G'ommz'ssz'ancr of Patents. 

